The placement of medicinal liquid in a patient's eye tends to be both difficult and annoying, particularly where the medicinal liquid is being self-administered. The process of instilling eye drops using the vast majority of eye droppers on the market today tends to be awkward at its best. First, a patient's head is substantially reclined and the eye dropper inverted over the patient's head. Next, the patient must attempt to accurately position the tip of the dropper over the appropriate portion of the eye. Then, the patient squeezes the reservoir of the eye dropper to dispense the requisite number of eye drops.
Precise application of the liquid eye drop medicine is thwarted by a lack of correspondence between the end of the tip of the eye dropper and the point at which each eye drop actually releases from the tip. If the eye dropper is held in a substantially vertical position, a drop will tend to fall toward a point immediately below the opening in the tip of the dropper. However, most people tend to use an eye dropper rotated away from a perfectly inverted position. This is especially true for elderly patients and others who have limited wrist and shoulder range of motion and have difficulty locating the dropper directly over the eye. As the eye dropper is rotated away from vertical, droplets will have a tendency to wettably adhere to the exterior surface of the tip surrounding the opening. Each subsequent droplet will tend to roll further along the tip away from the opening before dropping from the tip. Consequently, the point of release for each droplet will be somewhat offset from the location of the opening in the end of the tip. Often a portion of the liquid will be wasted as it remains adherent to the surface of the tip and refuses to fall.
Since a patient typically uses the open end of the tip of the eye dropper as a targeting mechanism, eye drop instillation efficiency and accuracy is maintained so long as droplets release from a point adjacent the opening in the tip. Once this targeting mechanism fails, dispensed eye drops will more frequently fail to reach the eye, with some drops falling only partially within the eyelid and others falling completely outside the eye.
Recognizing that a portion of the intended dosage has missed its target, a patient may elect to administer a second or even third dosage. As a result, a patient may unintentionally administer an excessive volume of medicine. This overdose could itself prove detrimental to the patient. Further, the waste will prematurely consume the supplied prescription volume, thereby shortening the duration of treatment and potentially failing to adequately treat the condition for which the medicine was prescribed.
Many persons, particularly the elderly, are not physically able to effectively self-administer medicinal eye drops using existing droppers with basic tips. They may have cervical spine or muscular problems of the neck resulting in limited head motion. Hence, these individuals would have difficulty tilting their heads sufficiently to provide an adequate target for placement of the eye drops. Additionally, patients may have wrist, shoulder or other upper body mobility problems which preclude lifting their arms sufficiently to raise the eye dropper bottle over their heads to allow the eye drops to be dispensed from a more vertical position of the dropper. Further, many individuals may experience vertigo or dizziness while attempting to dispense eye drops with their heads tilted backward. As people age, they frequently experience inner ear changes which cause them to more easily lose their balance when their head is extended. Hence, asking an elderly person to self-administer eye drops using today's standard droppers may be awkward or impossible in many situations.
The precision release tip is of great help in instilling drops into the eyes of a patient by another individual. With the current eye droppers, one must hold the bottle in a near vertical manner in front of the patient's eye. This presents a more threatening gesture to the patient and the protective reflexes of the eye cause the patient to squeeze their eyelids, thus making it difficult to instill the drops. With the precision tip dropper, the bottle may be held in a more horizontal position and below the line of vision. When this is combined with retracting the lower eyelid, a drop can be instilled without any threat to the eye.
Most standard eye droppers described in the prior art are somewhat conically-shaped with a larger base end of the tip attached to a reservoir of liquid eye medication. The free end of the tip is penetrated by an opening through which each drop of liquid eye medication is discharged. With the distal end of a standard tip directed perfectly downward, an eye drop will likely drop from the opening in the tip to fall toward a point on the patient's eye directly below the opening of the tip.
As the tip is rotated from an inverted toward a more horizontal position, liquid flowing out the opening of the standard tip will have a tendency to spread over and wettably adhere to a portion of the exterior surface of the tip. Once the exterior surface of the tip becomes wetted by the liquid medication, each drop of liquid exiting the opening in the tip will have a greater tendency to flow along the previously wetted path by virtue of molecular adhesion. The greater the wetted area of the exterior surface of the tip, the greater the tendency for each droplet to flow along the wetted surface.
As each droplet flows along the wetted surface, the point of release from the tip moves farther away from the opening in the tip. The liquid exiting the opening in the tip will flow along the wetted surface to accumulate at a point adjacent the boundary between the wetted and dry portion of the tip. As the discharged liquid flows to this boundary, sufficient mass will accumulate until a drop forms and falls from a point adjacent the boundary. Consequently, the drops no longer fall from the end of the tip. Although a patient may have the end of the prior art tip located substantially directly above the eye, the drops will likely roll down the tip to release at a point away from the end of the tip and miss the eye.
Accordingly, a need exists for an eye dropper tip capable of maintaining correspondence between the opening in the end of the tip and the point of release for each droplet to allow a patient to accurately and effectively self-administer eye drops.